Estradiol and Progesterone Receptors in Human Breast Fibroadenomas

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Abstract
Estradiol and progesterone receptors (ER and PR) were studied in 46 breast fibroadenomas obtained at different periods of the menstrual cycle (n = 38) or from patients under combined estrÔgen-progestagen contraceptive (n = 4) or substitutive progestagen treatment for progesterone insufficiency (n = 4). Cytosolic andnuclear ER (ERc and ERn) increased throughout the follicular phaseand were at their maximal level in the preovulatory phase. They decreased during the luteal phase.PR levels were high in the follicular phase, especially in the cytosol (PRc). PRc then decreased while nuclear progesterone receptor (PRn) increased at thebeginning of the luteal phase. Thereafter, PRc andPRn decreased andremained low during the luteal phase. PRcand PRn levels in fibroadenomas rom patients under estrogen-progestagen therapy were similar to those found during thelutealphase of untreated patients. In patients receiving a substitutive progestagen treatment tocorrect progesterone insufficiency, PRn was markedly higher than PRc The existence of ER and PR in breast fibroadenomas and the variations in their levelsduring the menstrual cycle or under hormonal treatment provide valuable information on the hormone dependency of breast fibroadenoma.